Theory of resonance in magnetically inhomogeneous specimens and some useful calculations

By deliberately changing the magnetic susceptibility of parts of an inhomogeneous specimen it is possible to distinguish, by means of a frequency shift, the magnetic resonance spectral lines of a given nucleus within particular spatial regions from the spectral lines of identical nuclei in the rest of the specimen. This may be of particular importance when dealing with macroscopic biological specimens such as whole cells or plant stems where the known geometry of sphere or cylinder may be exploited to produce different magnetic fields inside and outside the specimen. The background theory is described and calculations are performed for particular cases of interest. The calculations are experimentally verified for a curved liquid/liquid interface using chemical-shift imaging spectroscopy.